Here is a template that you can use to get started with external runtimes.

External Runtime Structure Template

Here is a thread on how to use multiple external runtimes.  The structure is already created in the template. But the information in the thread is very valuable just the same.

http://forum.daz3d.com/viewtopic.php?t=9060

Here is a picture that shows where the various types of files go into a runtime:

http://www.daz3d.com/support/faq/index.php?id=94

It's a good idea to unzip and / or install (.exe files) to a directory on your desktop first. This way you can browse through the folders to see what is there and you can rename and organize them before you deposit them into your actual runtime folder(s).

"It is good to see ourselves as others see us. Try as we may, we are never
able to know ourselves fully as we are, especially the evil side of us.
This we can do only if we are not angry with our critics but will take in good
heart whatever they might have to say." - Ghandi